I went to a seed bomb making workshop in Rio de Janeiro... They wrapped up the seed and soil mix in a little clay ball like a pastry parcel so that it takes a while for the outer layer to melt away (so you know there's definitely been some good rain). I guess that's an important factor in drier climes.

He he, every time I write the word seed bomb I imagine a little red light going off in some anti-terror ism detector bot. I hope a SWAT team doesn't crash through my door now, he he. I'll have to get my seed ninja skills up to scratch in preparation.